Search

MgO nanoparticles have good As-adsorption capacity in treating As-contaminated wastewater but suffer from high production cost. In this study, instead of using pre-formed MgO nanoparticles, we found that in-situ formed Mg(OH)2 from MgCl2 and NaOH reaction exhibited super high arsenate (As(V)) removal efficiency. Only 1.5 mmol/L of in-situ formed Mg(OH)2 could remove more than 95% As(V) within 10 min to make the As contaminated water (10 mg-As(V)/L) meet the municipal wastewater treatment standard, whereas MgO nanoparticles failed. The Mg-As sludge has an amorphous crystal structure while no Mg(OH)2 phase could be observed. As(V) existed uniformly within the sludge which was confirmed by elemental mapping. A precipitation-adsorption-coagulation mechanism might exist, which could relieve the restriction of limited surface area of solid MgO adsorbents. This study not only reveals an applicable method for efficient removal of trace level As(V) from water but also implies the huge potential of in-situ formed adsorbents in water treatment. [ABSTRACT FROM AUTHOR]

BACKGROUND: Including seaweed in cattle feed has gained increased interest, but it is important to take into account that the concentration of toxic metals, especially arsenic, is high in seaweed. This study investigated the arsenic species in milk from seaweed‐fed cows. RESULTS: Total arsenic in milk of control diets (9.3 ± 1.0 μg As kg−1, n = 4, dry mass) was significantly higher than seaweed‐based diet (high‐seaweed diet: 7.8 ± 0.4 μg As kg−1, P < 0.05, n = 4, dry mass; low‐seaweed diet: 6.2 ± 1.0 μg As kg−1, P < 0.01, n = 4, dry mass). Arsenic speciation showed that the main species present were arsenobetaine (AB) and arsenate (As(V)) (37% and 24% of the total arsenic, respectively). Trace amounts of dimethylarsinic acid (DMA) and arsenocholine (AC) have also been detected in milk. Apart from arsenate being significantly lower (P < 0.001) in milk from seaweed‐fed cows than in milk from the control group, other arsenic species showed no significant differences between groups. CONCLUSION: The lower total arsenic and arsenate in seaweed diet groups indicates a possible competition of uptake between arsenate and phosphate, and the presence of AC indicates that a reduction of AB occurred in the digestive tract. Feeding a seaweed blend (91% Ascophyllum nodosum and 9% Laminaria digitata) does not raise As‐related safety concerns for milk. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Abstract MgO nanoparticles have good As-adsorption capacity in treating As-contaminated wastewater but suffer from high production cost. In this study, instead of using pre-formed MgO nanoparticles, we found that in-situ formed Mg(OH)2 from MgCl2 and NaOH reaction exhibited super high arsenate (As(V)) removal efficiency. Only 1.5 mmol/L of in-situ formed Mg(OH)2 could remove more than 95% As(V) within 10 min to make the As contaminated water (10 mg-As(V)/L) meet the municipal wastewater treatment standard, whereas MgO nanoparticles failed. The Mg-As sludge has an amorphous crystal structure while no Mg(OH)2 phase could be observed. As(V) existed uniformly within the sludge which was confirmed by elemental mapping. A precipitation-adsorption-coagulation mechanism might exist, which could relieve the restriction of limited surface area of solid MgO adsorbents. This study not only reveals an applicable method for efficient removal of trace level As(V) from water but also implies the huge potential of in-situ formed adsorbents in water treatment.

Arsenic poisoning of groundwater is one of the most critical environmental hazards on Earth. Therefore, the practical and proper treatment of arsenic in water requires more attention to ensure safe drinking water. The World Health Organization (WHO) sets guidelines for 10 μg/L of arsenic in drinking water, and direct long-term exposure to arsenic in drinking water beyond this value causes severe health hazards to individuals. Numerous studies have confirmed the adverse effects of arsenic after long-term consumption of arsenic-contaminated water. Here, technologies for the remediation of arsenic from water are highlighted for the purpose of understanding the need for a single-point solution for the treatment of As(III)-contaminated water. As(III) species are neutral at neutral pH; the solution requires transformation technology for its complete removal. In this critical review, emphasis was placed on single-step technologies with multiple functions to remediate arsenic from water. [ABSTRACT FROM AUTHOR]

The co‐occurrence of fluoride and arsenate in groundwater is a growing global concern owing to their synergistic adverse effect on human health. Thus, development of materials capable of capturing fluoride and arsenate simultaneously from aqueous medium is of much need. Moreover, it is a matter of great research importance to develop sustainable adsorbents by recycling solid wastes. Keeping this in mind, herein a novel pseudoboehmite nanoparticles (PBN) were synthesized by chemical valorization of disposable waste aluminium pan for simultaneous removal of fluoride and arsenate in aqueous medium. The physicochemical properties of the material were confirmed using analytical techniques such as XRD, BET, FT‐IR, FESEM etc. Batch study confirms the maximum monolayer adsorption of 90.10 mg g−1 and 94.84 mg g−1 of fluoride and arsenate respectively, which shows comparable affinity of the material for both contaminants. The selectivity of the adsorbent towards fluoride and arsenate was further evaluated by set of kinetic experiments in both single‐ion and mixture‐ion environment. The synthesis of pseudoboehmite nanomaterial using disposal waste Al pan and its high efficacy for removal of fluoride and arsenic even in presence of competing anionic environments provide a new direction of waste management for sustainable remediation of groundwater contaminants. [ABSTRACT FROM AUTHOR]

The leaching of contaminants is a complex, pivotal process for understanding how biochar can immobilize them effectively. In this study, we investigated the impact of biochar, produced at different temperatures, on the behavior of arsenic (As) and lead (Pb) in leached sediments. Before leaching, we combined biochar with sediment, allowing it to naturally age for 365 days. The biochar derived from sugarcane straw was pyrolyzed at 350 °C (BC350), 550 °C (BC550), and 750 °C (BC750). Using UV–Vis spectroscopy, we assessed changes in dissolved organic carbon quality and examined geochemical alterations employing high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC–ICP-MS). The addition of biochar decreased Pb mobility while increasing As mobility. The extent of immobilization varied depending on the pyrolysis temperature: BC750 notably reduced Pb leaching by 54%, whereas BC350 enhanced As mobility by 2.5 times. Although no leaching of monomethylarsonic or dimethylarsinic acids occurred, both BC350 and BC750 amplified As3+ leaching by 2.5 times. In summary, biochar addition at different temperatures altered the environmental fate of As and Pb. Higher pyrolysis temperatures, as seen with BC750, were more effective in mitigating Pb mobility, reducing sediment leaching by 54%. Interestingly, exogenous dissolved organic carbon and phosphorus promoted As leaching.Highlights: Biochar temp influenced As/Pb mobility in sediment. 750 °C pyrolysis notably reduced Pb leaching by 54%. Lower temperature (350 °C) increased As mobility 2.5 times. External carbon/phosphorus boosted As leaching. 550 °C biochar was more effective against As3+ leaching. [ABSTRACT FROM AUTHOR]

• Ferrihydrite-biochar composite simultaneously removed Cd(II) and As(V). • As(V) presence promoted Cd(II) retention in the ferrihydrite-biochar composite. • The distribution of Cd(II)/As(V) in single system is different in the ferrihydrite-biochar composite. • Cd(II) and As(V) were closely associated with ferrihydrite in the mixed Cd&As system. The coexistence of cadmium (Cd(II)) and arsenate (As(V)) pollution has long been an environmental problem. Biochar, a porous carbonaceous material with tunable functionality, has been used for the remediation of contaminated soils. However, it is still challenging for the dynamic quantification and mechanistic understanding of the simultaneous sequestration of multi-metals in biochar-engineered environment, especially in the presence of anions. In this study, ferrihydrite was coprecipitated with biochar to investigate how ferrihydrite-biochar composite affects the fate of heavy metals, especially in the coexistence of Cd(II) and As(V). In the solution system containing both Cd(II) and As(V), the maximum adsorption capacities of ferrihydrite-biochar composite for Cd(II) and As(V) reached 82.03 µmol/g and 531.53 µmol/g, respectively, much higher than those of the pure biochar (26.90 µmol/g for Cd(II), and 40.24 µmol/g for As(V)) and ferrihydrite (42.26 µmol/g for Cd(II), and 248.25 µmol/g for As(V)). Cd(II) adsorption increased in the presence of As(V), possibly due to the changes in composite surface charge in the presence of As(V), and the increased dispersion of ferrihydrite by biochar. Further microscopic and mechanistic results showed that Cd(II) complexed with both biochar and ferrihydrite, while As(V) was mainly complexed by ferrihydrite in the Cd(II) and As(V) coexistence system. Ferrihydrite posed vital importance for the co-adsorption of Cd(II) and As(V). The different distribution patterns revealed by this study help to a deeper understanding of the behaviors of cations and anions in the natural environment. [Display omitted] [ABSTRACT FROM AUTHOR]

The use of probiotic lactobacilli has been proposed as a strategy to mitigate damage associated with exposure to toxic metals. Their protective effect against cationic metal ions, such as those of mercury or lead, is believed to stem from their chelating and accumulating potential. However, their retention of anionic toxic metalloids, such as inorganic arsenic, is generally low. Through the construction of mutants in phosphate transporter genes (pst) in Lactiplantibacillus plantarum and Lacticaseibacillus paracasei strains, coupled with arsenate [As(V)] uptake and toxicity assays, we determined that the incorporation of As(V), which structurally resembles phosphate, is likely facilitated by phosphate transporters. Surprisingly, inactivation in Lc. paracasei of PhoP, the transcriptional regulator of the two-component system PhoPR, a signal transducer involved in phosphate sensing, led to an increased resistance to arsenite [As(III)]. In comparison to the wild type, the phoP strain exhibited no differences in the ability to retain As(III), and there were no observed changes in the oxidation of As(III) to the less toxic As(V). These results reinforce the idea that specific transport, and not unspecific cell retention, plays a role in As(V) biosorption by lactobacilli, while they reveal an unexpected phenotype for the lack of the pleiotropic regulator PhoP. [ABSTRACT FROM AUTHOR]

Groundwater contamination is a global concern that has detrimental effect on public health and the environment. Sustainable groundwater treatment technologies such as adsorption require attaining a high removal efficiency at a minimal cost. This study investigated the adsorption of arsenate from groundwater utilizing chitosan-coated bentonite (CCB) under a fixed-bed column setup. Fuzzy multi-objective optimization was applied to identify the most favorable conditions for process variables, including volumetric flow rate, initial arsenate concentration, and CCB dosage. Empirical models were employed to examine how initial concentration, flow rate, and adsorbent dosage affect adsorption capacity at breakthrough, energy consumption, and total operational cost during optimization. The ε-constraint process was used in identifying the Pareto frontier, effectively illustrating the trade-off between adsorption capacity at breakthrough and the cost of the fixed-bed system. The integration of fuzzy optimization for adsorption capacity and its total operating cost utilized the global solver function in LINGO 20 software. A crucial equation derived from the Box-Behnken design and a cost equation based on energy and material usage in the fixed-bed system was employed. The results from identifying the Pareto front determined boundary limits for adsorption capacity at breakthrough (ranging from 12.96 ± 0.19 to 12.34 ± 0.42 μg/g) and total operating cost (ranging from 955.83 to 1106.32 USD/kg). An overall satisfaction level of 35.46% was achieved in the fuzzy optimization process. This results in a compromise solution of 12.90 μg/g for adsorption capacity at breakthrough and 1052.96 USD/kg for total operating cost. Henceforth, this can allow a suitable strategic decision-making approach for key stakeholders in future applications of the adsorption fixed-bed system. [ABSTRACT FROM AUTHOR]

The new mineral naalasite (IMA2023–027), NaAl(AsO3OH)2⋅H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it is a secondary alteration phase associated with anhydrite, juansilvaite, magnesiokoritnigite and a lavendulan-like phase. Naalasite occurs in tightly intergrown aggregates and druses of equant crystals. Crystals are light to medium pink and transparent, with vitreous lustre and white streak. The Mohs hardness is ~3½. The density is 3.19(2) g⋅cm–3. Optically, naalasite is uniaxial (+), with ω = 1.630(3) and ɛ = 1.660(3) (white light). The empirical formula (based on 9 O apfu) is Na0.92Al0.61Fe3+0.39As2O9H4.07. Naalasite is trigonal, space group R 32, with cell parameters: a = 8.494(4), c = 26.430(13) Å, V = 1651.5(4) Å3 and Z = 9. The structure, refined to R 1 = 3.78% for 641 I > 2σ I reflections, is based on a loose 3D framework of alternating AsO3OH tetrahedra and AlO6 octahedra. The structure is topologically equivalent to that of nafeasite and can be regarded as its Al analogue, even though nafeasite is monoclinic with space group C 2. [ABSTRACT FROM AUTHOR]

Arsenic in drinking water threatens public health worldwide. Phytoremediation has brought new vitality to solve this problem. The aim of this work was to study the role of emergent macrophyte sweet flag (Acorus calamus L.) in phytoremediation of arsenate [As(V)] and arsenite [As(III)] from polluted water. For that, the methods of analytic chemistry and physiology were used. The results showed that As(III) could be removed by A. calamus more efficiently than As(V). The removal efficiencies of As(V) and As(III) both reached more than 95%. In As(V)- and As(III)-exposed A. calamus, the arsenic contents were much higher in root than in stem and leaf. The translocation factors of As(V) and As(III) were no more than 0.152. Both As(V) and As(III) were found in the whole plant, whereas dimethylarsinic acid (DMA, 0.06‒0.13 mg kg‒1) was only present in the aboveground part. As(V) was the main species in the As(V)-exposed plants (45.86–70.21%). As(III) was the main species in stem and leaf of As(III)-exposed plants (55.76–85.52%), while As(V) was still dominant in root. A. calamus could keep its green leaves during the 31 days of inorganic arsenic (iAs) exposure. However, iAs had a little inhibitory effect on biomass accumulation, and high-concentration iAs was beneficial to promote root growth. The concentrations of malondialdehyde (MDA) and hydrogen peroxide (H2O2), as well as the activity of catalase (CAT) were significantly higher in root than those in stem and leaf. The oxidative stress response of A. calamus to As(III) was more than that to As(V). The findings of this study indicated that A. calamus was regarded as a promising material for the phytoremediation of arsenic from water.Highlights: calamus L. exhibited high tolerance to As(III) and As(V). As(III) can be methylated to DMA in the aboveground part of A. calamus L. Most of arsenic was accumulated in the roots. High-concentration iAs was beneficial to promote root growth. [ABSTRACT FROM AUTHOR]

The arsenic adsorption performance of silicon (Si), iron (Fe), and magnesium (Mg) mixed hydrous oxide containing a Si: Fe: Mg metal composition ratio of 0.05:0.9:0.05 (SFM05905) was investigated. SFM05905 was synthesized by the co-precipitation method. Batch experiments on arsenic adsorption were conducted at various temperatures and concentrations. Adsorption isotherms models were represented by a linearized equations and were insensitive to temperature change. The anion selectivity of SFM05905 at single component was high for arsenite (III), arsenate (V), and phosphate (PO4), indicating that PO4 inhibits arsenic adsorption. The adsorption amount of As (III), As (V), and PO4 were compared using a column packed with granular SFM05905, and an aqueous solution was passed by a combination of several anions that are single, binary, and ternary adsorbate systems. As (III) had the highest adsorption amount; however, As (III) and PO4 were affected by each other under the ternary mixing condition. Although the adsorption amount of As (V) was smaller than that of As (III), it was not affected by other adsorbates in the column experiments. Finally, although the adsorption of both arsenic continued, the adsorbed PO4 gradually desorbed. [ABSTRACT FROM AUTHOR]

The contamination of water by arsenic (As) has emerged as a significant environmental concern due to its well-documented toxicity. Environmentally relevant concentrations of As have been reported to pose a considerable threat to fish. However, previous studies mainly focused on the impacts of As at environmentally relevant concentrations on adult fish, and limited information is available regarding its impacts on fish at early life stage. In this study, zebrafish embryos were employed to evaluate the environmental risks following exposure to different concentrations (0, 25, 50, 75 and 150 μg/L) of pentavalent arsenate (AsV) for 120 hours post fertilization. Our findings indicated that concentrations ≤ 150 μg/L AsV did not exert significant effects on survival or aberration; however, it conspicuously inhibited heart rate of zebrafish larvae. Furthermore, exposure to AsV significantly disrupted mRNA transcription of genes associated with cardiac development, and elongated the distance between the sinus venosus and bulbus arteriosus at 75 μg/L and 150 μg/L treatments. Additionally, AsV exposure enhanced superoxide dismutase (SOD) activity at 50, 75 and 150 μg/L treatments, and increased mRNA transcriptional levels of Cu/ZnSOD and MnSOD at 75 and 150 μg/L treatments. Concurrently, AsV suppressed metallothionein1 (MT1) and MT2 mRNA transcriptions while elevating heat shock protein70 mRNA transcription levels in zebrafish larvae resulting in elevated malondialdehyde (MDA) levels. These findings provide novel insights into the toxic effects exerted by low concentrations of AsV on fish at early life stage, thereby contributing to an exploration into the environmental risks associated with environmentally relevant concentrations.

Chitosan grafted on graphene oxide (CS/GO) composite was synthesized to incorporate in polycarbonate (PC) membrane to improve its antifouling and arsenate (AsV) removal capabilities. The FTIR analysis and zeta potential measurement confirmed fine amine groups of CS on GO sheets and their presence in the fabricated membranes. The influence of different content of CS/GO composite on the structural properties, AsV removal efficiency and fouling resistance characteristics of the membranes were explored. The results indicated that the porosity, water uptake, mechanical properties and hydrophilicity of the membranes are enhanced with an increase of CS/GO concentration up to 1.5 wt%. Moreover, the results showed that the pure water flux (PWF) was 45 L m–2 h−1 for neat PC membrane while it was significantly increased for the modified membranes except for 2.0 wt% CS/GO and the best case reached to 111 L m–2 h−1 for PC-CS/GO-1.5 membrane. The AsV rejection by modified membranes increased from 75.1% (PC-CS/GO-0.5) to 100% (PC-CS/GO-1.0). The rejection of humic acid (HA) in solution of HA-As mixing slightly decreased, however AsV rejection improved in this solution. Fouling resistance of the membranes assessed by 10 ppm HA solution filtration revealed that 1.5 wt% CS/GO membrane has the best antifouling property. [ABSTRACT FROM AUTHOR]

Current models for inorganic ion transport in porous media describe the adsorption–desorption processes mostly based on empirical adsorption isotherms or simple thermodynamic mechanisms, often overlooking the adsorption kinetics. This study introduces a novel unified reactive solute transport model framework that incorporates well-established surface complexation models to describe the adsorption–desorption of ions in the transport process and takes into full consideration the non-equilibrium adsorption, enabling the use of the same set of thermodynamic-kinetic parameters to accurately describe ion transport under different chemical conditions. To evaluate the constructed model, Cr(VI), P(V), and As(V) column transport experiments were carried out using goethite-coated sand as the porous medium. Kinetic constants derived from single-ion transport experiments accurately predicted the cotransport behaviors of Cr(VI), P(V), and As(V) under various flow chemistry conditions, especially the overshooting phenomena of Cr(VI) under P(V) and As(V) competition. The model framework can be easily incorporated into solute transport models with various surface complexation reactions to predict the fate and transport of ions under complexed chemical conditions without extensive parameterization, and thus is a useful complement to the current reactive transport model. [ABSTRACT FROM AUTHOR]

The potential of arsenic (As) tolerant and sensitive varieties of wheat (Triticum aestivum L.) has yet to be explored despite of alarming situation of arsenic toxicity. To fill this gap, the study aimed to explore the role of antioxidants, phytochelatins, and ascorbate–glutathione for As tolerance in wheat. A total of eight varieties were exposed to different arsenate treatments (0, 1, 5, 10, 50, 100, 200, 500, 1000, 2000, and 10,000 μM) initially to screen effective treatment as well as contrasting varieties via Weibull distribution frequency for further analysis. The Weibull analysis found 200 μM as the most effective treatment in the present study. Selected varieties were analyzed for accumulation of total As and As speciation, oxidative stress (malondialdehyde, hydrogen peroxide), antioxidants (superoxide dismutase, catalase, peroxidase), phytochelatins, and ascorbate–glutathione cycle (glutathione-S-transferase, glutathione reductase, glutathione peroxidase, ascorbate peroxidase). Tolerant varieties showed less accumulation and translocation of total As, arsenate, and arsenite to the shoots compared with sensitive varieties under 200 μM treatment. Low concentration in tolerant varieties correlated with better growth and development response. Tolerant varieties showed higher induction of metabolites (glutathione, phytochelatins) compared to sensitive ones. Furthermore, tolerant varieties showed better performance of antioxidant and ascorbate–glutathione cycle enzymes in response to As exposure. The findings of the present study provided great insight into the wheat tolerance mechanism upon As exposure between contrasting varieties. [ABSTRACT FROM AUTHOR]

Arsenic (As) toxicity hinders plant growth and productivity and poses human health concerns. However, silicon (Si) nutrition can help improve plant tolerance to abiotic stresses. This study evaluated the influence of Si application on plant growth and As accumulation in an As hyperaccumulator plant, Isatis (Isatis cappadocica Desv.) under As stress. Isatis seedlings were exposed to 0, 5, 25, 125, and 625 μM Na2HAsO4.7H2O (AsV) and NaAsO2 (AsIII) and then Si was applied as Na2SiO3 (1 and 2 mM). Plant exposure to As(V: 650 μM) and As(III: 125 µM) caused significant reduction in plant fresh weight by 31 and 42%, and photosynthetic pigments by 47 and 62%, respectively. The same treatments caused 37- and 4.2-fold increase in levels of reactive oxygen species. However, exogenous application of Si effectively mitigated As stress, and caused a decrease in shoot As concentration up to 15% and 21% in As(V) and As(III) treated plants, respectively. In this regard, Si application at 1 mM level was more effective. The Si-induced tolerance against As in Isatis was attributed to the activation of antioxidant defense system (increase in the activities of gluthatione-S-transferase and guaiacol peroxidase, carotenoids, proline and anthocyanin contents). In conclusion, Si application improved the As tolerance in Isatis plants by modulating plant growth, decreasing As accumulation and activating the antioxidant defense system. [ABSTRACT FROM AUTHOR]

Biomethylation is an effective means of arsenic detoxification by organisms living in aquatic environments. Ciliated protozoa (including Tetrahymena species) play an important role in the biochemical cycles of aquatic ecosystems and have a potential application in arsenic biotransformation. This study compared arsenic tolerance, accumulation, methylation, and efflux in 11 Tetrahymena species. Nineteen arsenite (As(III)) S-adenosylmethionine (SAM) methyltransferase (arsM) genes, of which 12 are new discoveries, were identified, and protein sequences were studied. We then constructed recombinant cell lines based on the Tetrahymena thermophila (T. thermophila) wild-type SB210 strain and expressed each of the 19 arsM genes under the control of the metal-responsive the MTT1 promoter. In the presence of Cd2+ and As(V), expression of the arsM genes in the recombinant cell lines was much higher than in the donor species. Evaluation of the recombinant cell line identified one with ultra-high arsenic methylation enzyme activity, significantly higher arsenic methylation capacity and much faster methylation rate than other reported arsenic methylated organisms, which methylated 89% of arsenic within 6.5 h. It also had an excellent capacity for the arsenic detoxification of lake water containing As(V), 56% of arsenic was methylated at 250 μg/L As(V) in 48 h. This study has made a significant contribution to our knowledge on arsenic metabolism in protozoa and demonstrates the great potential to use Tetrahymena species in the arsenic biotransformation of aquatic environments.

Background: Arsenic (As) contributes to metabolic disorders, including diabetes, and disrupts the functions of multiple systems, leading to associated diseases and dysfunctions. This study aims to investigate the effects of Arsenic on plasma and liver enzymes, assess liver tissue histopathological changes, and explore spirulina's potential protective role against As-induced liver damage. Materials and Methods: Female Wistar rats were divided into six groups, including control, sodium arsenate-only (5mg/kg body weight), Sp-only (300mg and 600mg), and combined As and Sp treatment groups. Plasma and liver samples were collected after four weeks of treatment for enzyme analysis, and part of the liver tissues were examined histologically. Results: Arsenic exposure significantly increased aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) enzyme levels in plasma and liver. However, Sp supplementation at different doses showed a reduction in enzyme levels, although not statistically significant. Histological examination revealed liver damage in the As-exposed group, including congestion, leukocyte infiltration, and endothelium detachment. Sp supplementation partially attenuated these changes. Conclusion: This study enhances understanding of As's toxic effects and suggests that Sp supplementation may offer some protection against Asinduced liver damage. Recommendation: To improve the findings, additional parameters such as oxidative stress markers, inflammatory markers, and liver function tests should be incorporated. These measurements will provide a more comprehensive understanding of the effects of arsenate exposure. [ABSTRACT FROM AUTHOR]

There are many areas in the world where ground water has been contaminated by arsenic. MnO2 is one of the most inexpensive materials which can both adsorb arsenic and oxide arsenite [As(III)] to arsenate [As(V)]. In this study, the Ultra-long α-MnO2 nanowires with the (1 1 0) surface are used to remove As(III) and As(V) from solutions under different conditions. The adsorption kinetics for both As(III) and As(V) fit well with the pseudo-second-order kinetic model. For example, the pseudo-second-order adsorption kinetic constants are 0.076 × 103 and 0.077 × 103 g μg−1 min−1 at pH 7 for As(III) and As(V), respectively. At the same time, compared to the Freundlich model the Langmuir model better describes the adsorption equilibrium isotherms. For example, the maximum adsorption capacity values of the α-MnO2 nanowires obtained from the Langmuir model are 1.012 × 103 and 1.158 × 103 μg g−1 at pH 7 for As(III) and As(V), respectively. The adsorption capacities of α-MnO2 nanowires are affected by the pH value and increase with the initial arsenic concentration. Furthermore, the As(III) oxidation rate can be denoted by the pseudo-zero-order kinetic model and is related to O2 concentration, the light source used, the initial concentration of As(III), and the pH value. For example, the pseudo-zero-order kinetic equation is y = −0.90x + 163.6 with 4 L min−1 of O2, dark condition, 0.2 × 103 μg L−1 of As(III) and at pH 7. Finally, the oxidation mechanism is investigated and the oxidant in this reaction should be related with O2 not Mn(II). Besides its special structure and easy separation ability, it is a promising material to remove arsenic from water. [ABSTRACT FROM AUTHOR]

A new occurrence of austinite, CaZnAsO4(OH), conichalcite, CaCuAsO4(OH), and zincolivenite, CuZnAsO4(OH), is described from the Tripi mine, Peloritani Mountains, Sicily, Italy. These species have been observed in euhedral crystals in vugs of a calcite vein and were characterised using single-crystal X-ray diffraction, electron microprobe analysis and micro-Raman spectroscopy. Austinite and conichalcite have isotypic relations, both crystallising in space group P 212121. Unit-cell parameters of austinite are a = 7.4931(5), b = 9.0256(6), c = 5.9155(4) Å, V = 400.06(5) Å3; its crystal structure was refined on the basis of 1210 unique reflections with F o > 4σ(F o) and 77 least-square parameters to R 1 = 0.0236. Conichalcite has unit-cell parameters a = 7.419(10), b = 9.111(11), c = 5.867(7) Å and V = 396.6(1.4) Å3; the diffraction quality of its available grains was not good enough to allow a high-quality structural refinement. Chemical formulae of austinite and conichalcite are Ca1.04(1)Zn0.86(4)Cu0.09(4)As0.98(2)P0.02(1)O4(OH)0.98 and Ca0.98(1)Fe2+0.02(4)Cu0.69(10)Zn0.30(6)As0.97(2)P0.03(1)O4(OH)0.98, respectively. The new chemical data on the austinite–conichalcite isotypic pair, coupled with previous analyses, supports a possible miscibility gap between the compositions (Zn0.25Cu0.75) and (Zn0.50Cu0.50). Zincolivenite has unit-cell parameters a = 8.4594(9), b = 8.5324(8), c = 5.9893(6) Å, V = 432.30(12) Å3 and space group Pnnm ; its crystal structure was refined to R 1 = 0.0230 for 523 unique reflections with F o > 4σ(F o) and 47 least-square parameters. Its chemical composition is Cu0.73(5)Zn1.25(5)As1.01(1)O4(OH)1.01. The refinement of the crystal structure supports the ordering of Cu and Zn in two different crystallographic sites. Micro-Raman spectra of austinite, conichalcite and zincolivenite are discussed, with a focus on the O–H stretching region where local Zn and Cu arrangements affect the position of Raman bands in zincolivenite. These arsenates probably play an environmental role in the Peloritani area, where the occurrence of high contents of some potentially toxic elements in soils and stream sediments has been reported. [ABSTRACT FROM AUTHOR]

Wastewater from the uranium mining industry contains toxic arsenate (AsO43–), selenate (SeO42–), and molybdate (MoO42–) that can be removed by complexation with MgAlFe(III)CO3SO4 hydrotalcites, yet underlying mechanisms are poorly known. Here, we studied complexation by K–edge Extended X-ray Absorption Fine Structure Spectroscopy, Density Functional Theory, Powder X-ray Diffraction, and Infrared and Raman Spectroscopy. We found that single shell paths with a coordination number of 4 and bond lengths of As–O = 1.69 Å, Se–O = 1.65 Å and Mo–O = 1.76 Å were best fitted for As–MgAlFe, Se–MgAlFe, and Mo–MgAlFe hydrotalcites. We observed a single antisymmetric υ3 band with no splitting at 821 cm−1 for AsO43–, 856 cm−1 for SeO42–, and 852 cm−1 for MoO42–. In all cases, basal (d003) and interlayer (d006) spacings before and after anion adsorption varied by less than 0.1 Å. Therefore, our findings demonstrate that arsenate, selenate, molybdate form outer-sphere-like complexes with MgAlFe hydrotalcite, and that these complexes are surface-bound and not intercalated. [ABSTRACT FROM AUTHOR]

Fixed-bed columns packed with chitosan-magnetite (ChM) hydrogel and chitosan (Ch) hydrogel were used for the removal of arsenate ions from aqueous solutions at a pH of 7.0. The effect of flow rate (13, 20, and 25 mL/h), height of the columns (13 and 33 cm), and initial arsenate concentration (2, 5 and 10 mg/L) on the column's efficiency for the removal of As(V) is reported. The maximum adsorption capacity (qb), obtained before the allowed concentration of contaminant is exceeded, the adsorption capacity (qe) when the column is exhausted, and the mass transfer zone were determined. With this information, the efficiency of the column was calculated, which is given by the HL/HLUB ratio. The higher this ratio, the higher the efficiency of the column. The highest efficiency and the highest uptake capacity value at breakthrough point were obtained when using the lower flow rate, lower initial arsenate concentration, and longer bed length. When 33 cm-high columns were fed with a 10 mg As(V)/L solution at 13 mL/h, the maximum uptake capacity values at exhaustion obtained for Ch and ChM were 1.24 and 3.84 mg/g, respectively. A pH increase of the solution at the column's exit was observed and is attributed to the proton transfer from the aqueous solution to the amino and hydroxyl groups of chitosan. The incorporation of magnetite into Ch hydrogels significantly increases their capacity to remove As(V) due to the formation of complexes between arsenic and the magnetite surface. Experimental data were fitted to the Thomas model, the Yoon–Nelson model and the Bohart–Adams model using non-linear regression analysis. [ABSTRACT FROM AUTHOR]

Rice is a worldwide cultivated crop that serves as an important source of food for the human population, but it is also the simplest route for arsenic (As) contamination of the food chain. The As inorganic forms, arsenate [As(V)] and arsenite [As(III)], are the highly toxic As species found in the soil and the most easily absorbed by the roots. The absorption of As(V) prevails in aerobic soils while that of As(III) is favored in anaerobic soils. As(V) is converted to As(III) in the roots, although small amounts of As(V) also remain in the plant organs. The root system is the first target of the action of both As forms. The mechanisms of action of As(V) and As(III) are still widely unknown. Understanding them is essential for selecting rice genotypes with a lower capacity of As uptake and transport to the caryopses, thus improving food safety. Auxin is the phytohormone necessary for the development and plasticity of the root system, and its action is modulated by endogenous/exogenous brassinosteroids (BRs), mainly under stress conditions. The research aim was to deepen the knowledge of the mechanisms triggered by As(III) or As(V) in rice roots with particular attention to the role played by the interaction between auxin transport and BRs. We show that As(III) is the main As species present in rice roots regardless of the As(III) or As(V) forms supplied to the growing medium. Arsenic alters auxin distribution in both adventitious and lateral roots, but strongly in the latter ones. The application of an exogenous BR, the 24-epibrassinolide (eBL), combined with As(III) or As(V) strongly increases the expression of the OsPIN2 and OsAUX1 genes involved in auxin transport, thus contributing to restore the correct auxin distribution altered by As, and mainly by As(III), with higher effects on the LRs. Moreover, eBL increases the antioxidant activity in the roots in the presence of As, but only when combined with As(V).

The use of probiotic lactobacilli has been proposed as a strategy to mitigate damage associated with exposure to toxic metals. Their protective effect against cationic metal ions, such as those of mercury or lead, is believed to stem from their chelating and accumulating potential. However, their retention of anionic toxic metalloids, such as inorganic arsenic, is generally low. Through the construction of mutants in phosphate transporter genes (pst) in Lactiplantibacillus plantarum and Lacticaseibacillus paracasei strains, coupled with arsenate [As(V)] uptake and toxicity assays, we determined that the incorporation of As(V), which structurally resembles phosphate, is likely facilitated by phosphate transporters. Surprisingly, inactivation in Lc. paracasei of PhoP, the transcriptional regulator of the two-component system PhoPR, a signal transducer involved in phosphate sensing, led to an increased resistance to arsenite [As(III)]. In comparison to the wild type, the phoP strain exhibited no differences in the ability to retain As(III), and there were no observed changes in the oxidation of As(III) to the less toxic As(V). These results reinforce the idea that specific transport, and not unspecific cell retention, plays a role in As(V) biosorption by lactobacilli, while they reveal an unexpected phenotype for the lack of the pleiotropic regulator PhoP.

The arsenic adsorption performance of silicon (Si), iron (Fe), and magnesium (Mg) mixed hydrous oxide containing a Si: Fe: Mg metal composition ratio of 0.05:0.9:0.05 (SFM05905) was investigated. SFM05905 was synthesized by the co-precipitation method. Batch experiments on arsenic adsorption were conducted at various temperatures and concentrations. Adsorption isotherms models were represented by a linearized equations and were insensitive to temperature change. The anion selectivity of SFM05905 at single component was high for arsenite (III), arsenate (V), and phosphate (PO4), indicating that PO4 inhibits arsenic adsorption. The adsorption amount of As (III), As (V), and PO4 were compared using a column packed with granular SFM05905, and an aqueous solution was passed by a combination of several anions that are single, binary, and ternary adsorbate systems. As (III) had the highest adsorption amount; however, As (III) and PO4 were affected by each other under the ternary mixing condition. Although the adsorption amount of As (V) was smaller than that of As (III), it was not affected by other adsorbates in the column experiments. Finally, although the adsorption of both arsenic continued, the adsorbed PO4 gradually desorbed.

Arsenic (As) is a toxic heavy metal widely found in the environment that severely undermines the integrity of water resources. Bioremediation of toxic compounds is an appellative sustainable technology with a balanced cost-effective setup. To pave the way for the potential use of Deinococcus indicus, an arsenic resistant bacterium, as a platform for arsenic bioremediation, an extensive characterization of its resistance to cellular insults is paramount. A comparative analysis of D. indicus cells grown in two rich nutrient media conditions (M53 and TGY) revealed distinct resistance patterns when cells are subjected to stress via UV-C and methyl viologen (MV). Cells grown in M53 demonstrated higher resistance to both UV-C and MV. Moreover, cells grow to higher density upon exposure to 25 mM As(V) in M53 in comparison with TGY. This analysis is pivotal for the culture of microbial species in batch culture bioreactors for bioremediation purposes. We also demonstrate for the first time the presence of polyphosphate granules in D. indicus which are also found in a few Deinococcus species. To extend our analysis, we also characterized DiArsC2 (arsenate reductase) involved in arsenic detoxification and structurally determined different states, revealing the structural evidence for a catalytic cysteine triple redox system. These results contribute for our understanding into the D. indicus resistance mechanism against stress conditions. [ABSTRACT FROM AUTHOR]

In recent years, the impurity content in copper concentrate increases gradually with the consumption of high-grade copper ore. When the arsenic content in the raw materials increases, large amounts of arsenic enter the sulfuric acid system, resulting in large amounts of waste acid that put great pressure on production and environmental protection. Using the distribution characteristics of arsenic in each phase, the possibility of enriching arsenic in the form of stable arsenates in the slag was investigated to enrich arsenic in the form of stable arsenates in the slag. It is shown that increasing CaO content in slag at relatively low temperatures, controlling the slag type and changing the slag composition effectively improved the ability of the slag to absorb arsenic. Based on a theoretical analysis used to optimize the process parameters and determine a reasonable slag type, an oxygen-enriched top-blown smelting experiment was conducted with mixed copper concentrates. The mechanism of arsenic fixation in smelting slag at a smelting temperature of 1180 °C (1453 K) was investigated, and the results showed that the As content in slag was increased by 20∼50% and decreased by 10∼30% and 10∼20% in the dust and matte, respectively. Thus, arsenic is fixed in silicate in the form of stable arsenate, which can be an effective and safe treatment solution for copper smelting processes. [ABSTRACT FROM AUTHOR]

Contamination of paddy soils with arsenic (As) can cause phytotoxicity in rice and increase the accumulation of arsenic in grains. The uptake and accumulation of As in rice depends on the different As species present in the soil. Plants detoxify As by conjugating and sequestering xenobiotic compounds into vacuoles using various enzymes. However, the severity of damage induced by arsenite (As(III)) and arsenate (As(V)), as well as the roles of glutathione S-transferase in detoxifying these As species in rice, are not fully understood. In this study, we developed plant materials overexpressing a glutathione S-transferase gene OsGSTU40 under the control of the maize UBIL promoter. Through systematic investigations of both wild-type Nipponbare (Oryza sativa L., ssp. japonica) and OsGSTU40 overexpression lines under chronic or acute stress of As, we aimed to understand the toxic effects of both As(III) and As(V) on rice plants at the vegetative growth stage. We hypothesized that (i) As(III) and As(V) have different toxic effects on rice plants and (ii) OsGSTU40 played positive roles in As toxicity tolerance. Our results showed that As(III) was more detrimental to plant growth than As(V) in terms of plant growth, biomass, and lipid peroxidation in both chronic and acute exposure. Furthermore, overexpression of OsGSTU40 led to better plant growth even though uptake of As(V), but not As(III), into shoots was enhanced in transgenic plants. In acute As(III) stress, transgenic plants exhibited a lower level of lipid peroxidation than wild-type plants. The element composition of plants was dominated by the different As stress treatments rather than by the genotype, while the As concentration was negatively correlated with phosphorus and silicon. Overall, our findings suggest that As(III) is more toxic to plants than As(V) and that glutathione S-transferase OsGSTU40 differentially affects plant reactions and tolerance to different species of arsenic. [ABSTRACT FROM AUTHOR]

The optimal conditions for the green synthesis of nano zero-valent iron (G-NZVI) using mango peel extract were investigated using a Box-Behnken design approach. Three factors were considered, namely the ratio of iron solution to mango peel extract ratio (1:1–1:3), feeding rate of mango peel extract (1–5 mL min−1), and agitation speed (300–350 rpm). The results showed that the optimal conditions for the synthesis of G-NZVI for arsenate removal were a 1:1 ratio of iron solution to mango peel extract, a mango peel extract feeding rate of 5 mL min−1, and an agitation speed of 300 rpm. Under these conditions, nearly 100% arsenate removal was achieved. X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), and scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDX) methods were used to characterize the properties of the G-NZVI. Finally, the arsenate removal efficiency of the G-NZVI was compared against that of commercial nano zero-valent iron (C-NZVI). The results revealed that the G-NZVI was roughly five times more efficient at arsenate removal than the C-NZVI. The influence of background species such as chloride (Cl−), phosphate (PO43−), calcium (Ca2+), and sulfate (SO42−) was studied to evaluate their effects on arsenate removal. As a result, Cl− and Ca2+ were shown to play a role in promoting arsenate removal, whereas SO42− and PO43− were observed to play an inhibiting role. [ABSTRACT FROM AUTHOR]

Heavy metals in water pose a great threat to human health, and water treatment remains a critical issue globally. Among various water treatment techniques, adsorption has been proven to be an excellent way to remove heavy metals from water due to its advantages, like low cost, availability, profitability, ease of operation, and efficiency. Heavy metals such as chromium and arsenic are present in water in the form of anions, while many common adsorbents, such as biochar and activated carbons, cellulose, chitosan, clays, and silica, tend to acquire a negative surface charge. The surface charge of the adsorbent plays a major role in its interaction with heavy metal ions. Polyethylenimine is a polymer with a high cationic charge density. Modification of these adsorbents with polyethylenimine results in higher selectivity for these anions. The adsorption capacity is related to the efficiency of the introduction of polyethylenimine, which depends on the surface properties of the adsorbent. This review focuses on the effect of modification with polyethylenimine on the adsorption capacity of common adsorbents for the removal of heavy metal ions, such as chromate and arsenate, from water. [ABSTRACT FROM AUTHOR]

Highly sensitive and selective chemosensors N2R1–N2R3 for detecting water-polluting inorganic arsenic anions, arsenite, and arsenate were synthesized and characterized. The selectivity of anions was studied in the pure organic media as well as the organo-aqueous media. Receptors N2R1 and N2R3 exhibited selectivity toward arsenite ion over arsenate ion in the acetonitrile media with a Limit of Detection (LOD) of 0.119 ppm and 0.323 ppm, respectively. In 30% aq. DMSO, receptors N2R1–N2R3 displayed selectivity toward arsenite and arsenate with a better LOD of 0.044 ppm. The anion binding to the receptor achieved a spectral absorption shift toward the near-infrared region in both organic and aqueous media, making the receptors better colorimetric sensors. The cyclic voltammetric investigations, 1H–NMR titration, UV–Vis titration, and DFT experiments provided strong evidence for the initial H-bonding upon interaction with the anions and the subsequent deprotonation pathway for the detection of inorganic arsenic anions. [ABSTRACT FROM AUTHOR]

The aim of this work is to isolate the microbes possessing arsenic degrading property from contaminated soil, collected from Cauvery River at Pallipalayam, Erode District. Six microbial strains were grown well in 40Mm sodium arsenate as a sole carbon source amended M9 minimal media. Based on the zone of clearance, three microbial strains were found to be potent arsenic degrading microbes and they are identified as Bacillus spp., Staphylococcus spp., and Pseudomonas spp. They may potentially be used in the bioremediation of arsenic and other contaminants. It infers that the presence of arsenate reductase (ArcC) gene in three of the microbial strain and they were taken for further studies. Genomic DNA isolation protocol was standardized and DNA isolation was performed. ArcC gene-specific primers were designed using Primer3 bioinformatics tool. Genetic diversity among the strains was studied by RAPD analysis using four different primers. Dendrogram was constructed using Unweighted Pair Group using Arithmetic Averages and NJ tools. The presence of genetic diversity was observed from the analysis. Polymerase chain reaction amplification and sequencing of amplified gene products are to be done in future. Background: The aim of this work is to isolate the microbes possessing arsenic degrading property from contaminated soil, collected from Cauvery River at Pallipalayam, Erode District. Six microbial strains were grown well in 40Mm sodium arsenate as a sole carbon source amended M9 minimal media. Based on the zone of clearance, three microbial strains were found to be potent arsenic degrading microbes and they are identified as Bacillus spp., Staphylococcus spp., and Pseudomonas spp. They may potentially be used in the bioremediation of arsenic and other contaminants. It infers that the presence of arsenate reductase (ArcC) gene in three of the microbial strain and they were taken for further studies. Genomic DNA isolation protocol was standardized and DNA isolation was performed. ArcC gene-specific primers were designed using Primer3 bioinformatics tool. Genetic diversity among the strains was studied by RAPD analysis using four different primers. Dendrogram was constructed using Unweighted Pair Group using Arithmetic Averages and NJ tools.The presence of genetic diversity was observed from the analysis. Polymerase chain reaction amplification and sequencing of amplified gene products are to be done in future. Methods: The soil sample was collected from Cauvery River, Pallipalayam. Arsenate, arsenic bioremediation, arsenic reducing gene, RAPD, and genetic diversity were used. Results: With the dilution concentrations, 10−5 and 10−6 microbial population was obtained in M9 minimal media. From the pure colonies of isolates, TA1, TA2, TA4, and TA5 genomic DNA was extracted using the protocol mentioned above. The culture was inoculated in LB broth and kept in incubation at 37°C for overnight. From overnight culture, genomic DNA was extracted. RAPD analysis for the isolates was performed using four different random primers namely RBA-1, RBA-4, RBA-5, and RBA-6. Conclusion: Three of the isolates designated as TA2, TA4, and TA5 were found to be potent arsenic degarding microbes. They are able to degrade sodium arsenate of about 40mM. It infers that they can be potentially used in bioremediation of arsenic. Isolation of ArcC gene from the isolates is in progress. Sequencing will reveal the nature of amplified products. If the amplified genes are cloned and mass production of ArcC gene could be obtained.

Arsenic (As) is a toxic heavy metal widely found in the environment that severely undermines the integrity of water resources. Bioremediation of toxic compounds is an appellative sustainable technology with a balanced cost-effective setup. To pave the way for the potential use of Deinococcus indicus, an arsenic resistant bacterium, as a platform for arsenic bioremediation, an extensive characterization of its resistance to cellular insults is paramount. A comparative analysis of D. indicus cells grown in two rich nutrient media conditions (M53 and TGY) revealed distinct resistance patterns when cells are subjected to stress via UV-C and methyl viologen (MV). Cells grown in M53 demonstrated higher resistance to both UV-C and MV. Moreover, cells grow to higher density upon exposure to 25 mM As(V) in M53 in comparison with TGY. This analysis is pivotal for the culture of microbial species in batch culture bioreactors for bioremediation purposes. We also demonstrate for the first time the presence of polyphosphate granules in D. indicus which are also found in a few Deinococcus species. To extend our analysis, we also characterized DiArsC2 (arsenate reductase) involved in arsenic detoxification and structurally determined different states, revealing the structural evidence for a catalytic cysteine triple redox system. These results contribute for our understanding into the D. indicus resistance mechanism against stress conditions.

A magnetic mixed iron oxide, magnetite (Fe3O4), was synthesized in the laboratory and characterized before its use as sorbent for arsenic removal. The characterization techniques used were X-ray diffraction (XRD), specific surface area, zeta potential and particle size measurements. The sorbent was applied for arsenic removal, without any pre or post treatment, from groundwater. The efficiency of sorption can only be improved by understanding the sorbent–sorbate interaction. For onsite monitoring of the sorbent-sorbate interaction, an electrochemical investigation using cyclic voltammetry (CV) measurement was developed. The study confirmed that the sorption of As(III) on Fe3O4 is dynamic (reversible) whereas that of As(V) is static (irreversible) in nature. Detailed investigation after the sorption was carried out utilizing X-ray photoelectron spectroscopy (XPS) measurement. The complexation of As(III)-Fe3O4 and As(V)-Fe3O4 without any redox transformation was evident from the XPS data. By careful examination of the results, a mechanism of arsenic removal by Fe3O4 was proposed. [ABSTRACT FROM AUTHOR]

The new mineral alumolukrahnite (IMA2022–059), CaCu2+Al(AsO4)2(OH)(H2O), was found at the Jote mine, Copiapó Province, Chile, where it is a secondary alteration phase associated with conichalcite, coronadite, gypsum, olivenite, pharmacosiderite, rruffite and scorodite. Alumolukrahnite occurs as crude diamond-shaped tablets up to ~0.1 mm, intergrown in crude spherical aggregates. Crystals are apple green and transparent to translucent, with vitreous lustre and a white streak. The Mohs hardness is 3½. The mineral is brittle with irregular fracture and no cleavage. The calculated density is 4.094 g cm–3. Optically, alumolukrahnite is biaxial (+) with α = 1.73(1), β = 1.74(1) and γ = 1.76(1) (white light). The empirical formula, determined from electron microprobe analyses, is Ca1.01(Cu0.92Zn0.13)Σ1.05(Al0.96Fe0.01)Σ0.97(As0.985O4)2(OH)0.88(H2O)1.12. Alumolukrahnite is triclinic, P1 ¯, a = 5.343(5), b = 5.501(5), c = 7.329(5) Å, α = 67.72(2), β = 69.06(2), γ = 69.42(2)°, V = 180.3(3) ų and Z = 1. Alumolukrahnite is a member of the tsumcorite group and is the Al analogue of lukrahnite. [ABSTRACT FROM AUTHOR]

The steel industry in Taiwan produces more than 3 million tons of steelmaking slag per year on average. Conventional solidification and landfilling methods are no longer suitable for the highly populated small island as a wide area is needed for such methods. This study aims to improve the quality of polluted water bodies using desulfurization slag – a recycled product resulted from steelmaking – as an arsenate adsorbent. Experimental results revealed that desulfurization slag pH and metal ions including Ca, Mg, Fe, and Mn affected the behavior and content of arsenate existing in an aqueous solution. The concentration of Ca among these metal ions is the highest in the aqueous solution, which facilitates the formation of calcium hydroxyarsenate and is therefore more critically beneficial than other metal ions in removing As in the aqueous solution. Additionally, desulfurization slag samples with particle size of >200 mesh had a greater specific surface area compared to those in other particle sizes, suggesting preferable As adsorption ability of slag with higher mesh numbers. Such desulfurization slag samples were thus used in subsequent adsorption experiments in this study. The energy dispersive spectrometry results confirmed that the >200‐mesh group comprised the highest metal oxide content in terms of As removal. This study found that under different Cl− and SO42− concentrations, the covalent bond effect did not significantly affect the slag's ability to adsorb As. According to the adsorption isotherm experiment results, the Langmuir model (R2 = 0.998) outperformed the Freundlich model (R2 = 0.961) possibly because the former is suitable for situations with even energy distribution and monolayer adsorption, while the latter is often applied to scenarios with uneven distribution and multilayer adsorption, indicating that the adopted desulfurization slag adsorbed arsenate through the mechanism of monolayer adsorption. There are many useful contents in the desulfurization slag. In terms of sustainable use of resources, desulfurization slag is worthy of economic development and reusing if recycled. Currently, there is little research and information on desulfurization slag in Taiwan. Hopefully, this study will be helpful for future development and application of desulfurization slag in recycling techniques. [ABSTRACT FROM AUTHOR]

Arsenic (As) contamination is a major threat to drinking water quality throughout the world, and the development of appropriate remediation methods is critical. Adsorption is considered the most effective method for remediation of As-contaminated water. Biochar is a promising adsorbent and widely discussed for As removal due to its potential low cost and environmental friendliness. However, pristine biochar generally exhibited relatively low adsorption capacity for As mainly due to the electrostatic repulsion between the negatively charged biochar and As. Biochar modification, especially metal modification, was developed to boost the adsorption capacity for As. A systematic analysis of As removal as affected by biochar properties and modification will be of great help for As removal. This paper presents a comprehensive review on As removal by biochars from different feedstock, preparation procedures, and modification methods, with a major focus on the possible mechanisms of interaction between As and biochar. Biochar derived from sewage sludge exhibited relatively high adsorption capacity for As. Considering energy conservation, biochars prepared at 401–500 °C were more favorable in adsorbing As. Fe-modified biochar was the most popular modified biochar for As remediation due to its low cost and high efficiency. In addition, the limitations of the current studies and future perspectives are presented. The aim of this review is to provide guidance for the preparation of low-cost, environmentally friendly, and high efficiency biochar for the remediation of As-contaminated water. [ABSTRACT FROM AUTHOR]

Poorly-crystalline ferrihydrite is ubiquitous in the environment and contributes to controlling the fate of arsenic in sediments and soils. Although there is evidence that ferrihydrite has a higher affinity towards As(III) relative to As(V), little is known about how and why As(III) is readily immobilized by ferrihydrite. In this study, ferrihydrite was employed to evaluate the As(III) and As(V) adsorption behavior. The properties of ferrihydrite such as morphology, pore size distribution, arsenic adsorption species, and adsorption energies of arsenic at different sites were carefully examined using TEM-EDS mapping, positron annihilation lifetime (PAL) spectroscopy, X-ray absorption spectroscopy (XAS), N 2 adsorption isotherms, and theoretical calculations of density function theory (DFT). Batch adsorption experiments revealed that the maximum adsorption of As(III) (839.7 μmol g−1) on ferrihydrite, fitted by Langmuir model, was considerably larger than that of As(V) (372.4 μmol g−1). PAL characterization and pore size distribution analysis demonstrated that ferrihydrite had an abundance of vacancy cluster-like micropores, which consisted of 10–20 atom deficiencies (V 10-20). The calculated hydrated ion size of As(III) species (4.22 Å) at pH 6.0 was smaller than the size of As(V) (5.90 Å). The higher As(III) adsorption to ferrihydrite was attributed to its surface adsorption sites as well as its abundant micropore adsorption sites, which are available only to As(III) due to their size matching well with the size of the ferrihydrite micropores, thus significantly contributing to greater As(III) immobilization. [ABSTRACT FROM AUTHOR]

Here, we report a highly selective arsenite (As(III)) sensor based on gold nanoparticles (AuNPs) and ionic liquids (ILs). AuNPs were citrate-capped with negative charges on their surfaces, and could aggregate and precipitate once electrolytes were introduced to neutralize the negative charges. In this study, we discovered that organic ILs, behaving similarly to inorganic electrolytes such as NaCl, could induce the aggregation and precipitation of AuNPs much more efficiently than inorganic electrolytes. Since As(III) inhibited while ILs promoted the aggregation of AuNPs, we examined the interactions between AuNPs, As(III), and ILs and the possibility of using ILs and AuNPs as a sensing probe to detect arsenite and determine its concentration. Six different ILs were evaluated for this purpose in this study. Repeatability, interference, stability, selectivity, and sensitivity were investigated to evaluate the As(III) sensing probe. The limit of detection (LOD) of the sensor sBMP was as low as 0.18 ppb, ranked as the second lowest among the reported arsenite sensors. The sensing of arsenite was also demonstrated with real water samples and was cross-validated with ICP-OES. [ABSTRACT FROM AUTHOR]

We investigated the interaction of As(III) with As(III)-binding DNA aptamers (Ars-3). The binding of Ars-3 to As(III) was investigated using an Ars-3 sequence and a few control DNA sequences. As a result, we conclude that Ars-3 cannot bind As(III) and As(III) can adsorb onto gold nanoparticles with selectivity. However, the As(III) concentration could be determined by a simple As(III) analysis method using Ars-3, and we measured the As(III) and As(V) concentrations separately in As(III)/As(V) mixed samples in ultrapure water and groundwater using a simple analytical method for As(III) and As(V), respectively. As(III) in the sample was measured by a simple As(III) analytical method using DNA aptamers and gold nanoparticles, and As(V) in the sample was measured by a simple As(V) analysis method using cerium oxide nanoparticles and fluorescence-labeled DNA. We can measure As(III) and As(V) concentrations in ultrapure water and groundwater in the simple analytical method for As(III) and As(V), separately. HIGHLIGHTS We investigated the interaction between Ars-3 and As(III).; We determined As(III) and As(V) concentrations by simple analytical method for As(III) and As(V).; We hypothesized that the simple As(III) analysis method can quantify As(III) concentration by the adsorption of As(III) and ssDNA onto AuNPs.; We could determine the As(III) concentration and As(V) concentration in As(III)/As(V) mixed samples for each chemical species.;

The isostructural compounds caesium decasodium tetrazirconium nonaarsenate, CsNa10Zr4(AsO4)9, and caesium decasodium tetrahafnium nonaarsenate, CsNa10Hf4(AsO4)9, arose as unexpected single-crystal products from the reactions of Na2CO3, MO2 (M = Zr, Hf) and As2O5 in a eutectic flux of NaCl and CsCl. They consist of MO6 octahedra and AsO4 tetrahedra sharing vertices to generate three-dimensional polyhedral networks encapsulating the caesium and sodium ions. The MO6 groups share all their vertices with adjacent As atoms but the As atoms have one or two `terminal' O atoms not bonded to Zr or Hf. The Cs+ ion adopts a squashed octahedral geometry and the coordination polyhedra of the partially occupied sodium ions are variously trigonal bipyramidal, tetrahedral, square pyramidal and trigonal pyramidal. Site symmetries: Cs \overline{3}; M 3; As 1 and 2; O 1; Na 1, 2 and 3. The M = Zr crystal was refined as an obverse/reverse rhombohedral twin.

Little information is available on influences of the conversion of dissolved organic phosphorus (DOP) to inorganic phosphorus (IP) on algal growth and subsequent behaviors of arsenate (As(V)) in Microcystis aeruginosa (M. aeruginosa). In this study, the influences factors on the conversion of three typical DOP types including adenosine-5-triphosphate disodium salt (ATP), β-glycerophosphate sodium (βP) and D-glucose-6-phosphate disodium salt (GP) were investigated under different extracellular polymeric secretions (EPS) ratios from M. aeruginosa , and As(V) levels. Thus, algal growth, As(V) biotransformation and microcystins (MCs) release of M. aeruginosa were explored in the different converted DOP conditions compared with IP. Results showed that the three DOP to IP without EPS addition became in favor of algal growth during their conversion. Compared with IP, M. aeruginosa growth was thus facilitated in the three converted DOP conditions, subsequently resulting in potential algal bloom particularly at arsenic (As) contaminated water environment. Additionally, DOP after conversion could inhibit As accumulation in M. aeruginosa , thus intracellular As accumulation was lower in the converted DOP conditions than that in IP condition. As(V) biotransformation and MCs release in M. aeruginosa was impacted by different converted DOP with their different types. Specifically, DMA concentrations in media and As(III) ratios in algal cells were promoted in converted βP condition, indicating that the observed dissolved organic compositions from βP conversion could enhance As(V) reduction in M. aeruginosa and then accelerate DMA release. The obtained findings can provide better understanding of cyanobacteria blooms and As biotransformation in different DOP as the main phosphorus source. Graphical Abstract [Display omitted]. [ABSTRACT FROM AUTHOR]